All notifications for specific user are being deleted from database, when only one should be removed

Question

The problem that I am having is that I have written two different methods: 1 for adding a notification to the database, and 1 for removing that notification. You receive a notification is another user likes your post, comments on your post, likes your comment, etc. In those cases the user whose post it is will receive a notification letting them know that you have liked their comment, or their post, etc.

The issue is that the notifications are being saved to the database just fine, but when a user for example unlikes a post, not just that notification is deleted, but all of the notifications of that user. I am not sure why this is happening, I would just like that one notification with its specific notificationId to be removed from the database, not all of the notifications that user has received.

PostAdapter

holder.like.setOnClickListener(v -> {
            if (holder.like.getTag().equals("like")) {
                FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid()).child(mFirebaseUser.getUid()).setValue(true);
                addNotification(post.getPublisher(), post.getPostid());
            } else {
                FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid()).child(mFirebaseUser.getUid()).removeValue();
                deleteNotification(post.getPublisher());
            }
        });

 private void addNotification(final String userid, final String postid) {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Notifications").child(userid);

        String notificationId = reference.push().getKey();

        HashMap<String, Object> hashMap = new HashMap<>();
        hashMap.put("userid", mFirebaseUser.getUid());
        hashMap.put("comment", "liked your event");
        hashMap.put("postid", postid);
        hashMap.put("notificationId", notificationId);
        hashMap.put("ispost", true);

        if (notificationId != null)
            reference.child(notificationId).setValue(hashMap);
    }

    private void deleteNotification(String userid) {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Notifications").child(userid);
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    Notification notification = snapshot.getValue(Notification.class);
                    if (notification != null) {
                        reference.child(notification.getNotificationId()).removeValue();
                    }
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

Second method

holder.like.setOnClickListener(v -> {
        if (holder.like.getTag().equals("like")) {
                FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid()).child(mFirebaseUser.getUid()).setValue(true);
                addNotification(post.getPublisher(), post.getPostid());
            } else {
                FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid()).child(mFirebaseUser.getUid()).removeValue();
                FirebaseDatabase.getInstance().getReference().child("Notifications").child(post.getPublisher()).child(mNotificationId).removeValue();
            }
        });

private void addNotification(final String userid, final String postid) {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Notifications").child(userid);

        mNotificationId = reference.push().getKey();

        HashMap<String, Object> hashMap = new HashMap<>();
        hashMap.put("userid", mFirebaseUser.getUid());
        hashMap.put("comment", "liked your event");
        hashMap.put("postid", postid);
        hashMap.put("notificationId", mNotificationId);
        hashMap.put("ispost", true);

        reference.child(mNotificationId).setValue(hashMap);
    }

Answer 1

if (notification != null) {
     reference.child(notification.getNotificationId()).removeValue();
}

These lines should change. Because the notification id is never null and all notifications are deleted.

if (notification.getUserId().equals(mFirebaseUser.getUid())) {
     reference.child(notification.getNotificationId()).removeValue();
}

Or you can save the notification id using another way and delete the notificaition without checking all the notifications.

Add func:

private void addNotification(final String userid, final String postid) 
{
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Notifications").child(userid);

mNotificationId = reference.push().getKey();

HashMap<String, Object> hashMap = new HashMap<>();
hashMap.put("userid", mFirebaseUser.getUid());
hashMap.put("comment", "liked your event");
hashMap.put("postid", postid);
hashMap.put("notificationId", mNotificationId);
hashMap.put("ispost", true);

reference.child(mNotificationId).setValue(hashMap);

HashMap<String, Object> hashMap2 = new HashMap<>();
hashMap2.put("notificationId", mNotificationId);     
hashMap2.put("like", true);
FirebaseDatabase.getInstance().getReference().child("Likes").child(postid).child(mFirebaseUser.getUid()).setValue(hashMap2);
}

delete func:

 private void deleteNotification(String userid, final String postid)) {
 DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid()).child(mFirebaseUser.getUid());

 reference.addListenerForSingleValueEvent(new ValueEventListener() {
 @Override
 public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
    if (dataSnapshot.exists()){
          String notificationId = dataSnapshot.child("notificationId").getValue(String.class);

          FirebaseDatabase.getInstance().getReference("Notifications")
          .child(userid).child(notificationId).removeValue();
          reference.removeValue();
      }
 }

 @Override
 public void onCancelled(@NonNull DatabaseError databaseError) {

 }
 });
 }